Process of hydrometallurgically treating material containing lead and zinc values



March 19, 1929. w CQRBQULD- 1,706,143

PROCESS` OF HYDROMIEI'I'ALLURGI( JALLY` TRBAQ'IQG, MATERIAL CONTAINING LEAD AND A ZINC VALUES Filed March 51, 1926 J//mes I Ice/9c I Patented Mar. 19, 1929.

UNITED STATES PATENT QFFICE.

WILLIAM HENRY GORBOULD, OF SYDNEY, NEW .SOUTH THALES, AUSTRALIA.

PROCESS OFHYDROMETALLURGICALLY resserrer-a Meran-rer.- CONTMNING LEAD AND ZINC venues.

Application led March 31, 1926', Serial No. 98,930, and Australia July S8, 1925.

This invention relates to process in which oxide products of lead and/or Zinc, or oxidized lead ores containing Zinc, or mixed oxidized or sulphide ores of lead and Zinc are h vdrometallurgically treated for the purpose of obtaining therefrom the metallic constituents thereof separately, or for obtaining separately a concentrated product of lead or of zinc.

In the operation of the process the material to be treated is first 0round to a sufiicient state of fineness. If the material should contain lead carbonate, ferrous carbonate, Zinc carbonate, or sulphide of lead or sulphide of Zinc, or both said sulphides, it is first roasted in a furnace in the presence of heated airat a suitable variable temperature, such tempera-ture depending on the ore which is being treated. In such roasting, carbon dioxide and sulphur combined with the material operated on are expelled therefrom.

When operating on concentrated products of lead sulphide the sulphide of lead is roasted in a furnace at O0-550 C. when sulphide of lead is converted into sulphate of lead. Such roasted concentrates are then withdrawn from the furnace and allowed to cool when a calculated percentage of ammonium carbonate in excess is mixed therewith; the said mixture is then ground in a pan and when thoroughly subdivided and admixed, a small amount of water is added, and the grinding is continued until decomposition of the sulphate of lead is complete whereby carbonate of lead and sulphate of ammonia are formed; additional water is added and the soluble sulphate of ammonia and a little free ammonium carbonate filtered olf. The residue of oarbonate of lead is then given water washes to free it of sulphate of ammonia. The solution of sulphate of ammonia and wash waters are mixed together, and a little sulphuric acid is added to the mixture to decompose the free ammonium carbonate and to form sulphate of ammonia; then the whole is evaporated to dryness. rlhe dried sulphate of ammonia is mixed with ground carbonate of lime and transferred to an iron retort, heated to redness, and the vapors of ammonium carbonate are conducted to a lead chamber, condensed and made available for another cycle of operation. rlhe residue of carbonate of lead is now heated to about 3500 C. to convert the carbonate of lead into oxide of lead.

ln case the material to be treated does not contain any carbonates or sulphides it is not necessary to subject it to roasting. If, however, t-he material is roasted it is necessary to allow it to first cool before it is submitted to further treatment as is hereinafter described.

After the material has been ground, and, if

required, also roasted and cooled, or treated as above described to obtain an oxide product, such material or the oxide product is placed in a tank and water is added thereto, whereby a thin pulp is produced. The pulped ma- J.ferial is mechanically agitatec by suitable apparatus in said tank, whereby the soluble salts thereof are dissolved, and the material may then be passed over concentrating` tables or other mechanical appliance to separate it into sands and slimes.

lt is to be understood, however, that the separation of the material into sands and slimes is not essential in the treatment of all materials, as. in the case of certain materials to be treated, good results can be obtained without separating` the pulped material into sands and slimes, and leaching these products in separate tanks as hereinafter described; in the treatment of the particular materials referred to, it will be found sut'icient to grind saine to a suitable degree of ineness in some cases it is groun d to produce slimes only), and is then leached in one tank.

rlhe method of treatment of the material which is preferred wherein the pulp is separated into sands and slimes will now be described. l

rllhe sands are fed to a filter and deprived of their surplus water. The slimes are also fed to a filter and deprived of their surplus water content. Subsequently such sands and Slimes are each fed to Separate leaching tanks.

The dewatered slimes in the leaching tank are then subjected to treatment by circulating a calculated solution of acetic acid in water through the slimes, whereby a thin pulp of the slimes is produced and oxides of lead and zinc carried thereby are dissolved, and acetates of lead and zinc are thereby formed. rllhe percentage of acetic acid (100%) which is used in such treatment will be dependent on the percentage content of oxides of lead and Zinc which are present in the total combined said sands and slimes. It has been found by experiment that the proportion of acetic acid usable elfectively in the leaching treatment is approximately 0.3

-sary proportionate quantity of acetic acid must be provided for these impurities in the solution of acetic acid in water in addition to the acetic acid required for such solution in the treatment of the oxides of lead and zinc.

Such proportionate quantity of acetic acidis only determinable after a laboratory test has been made of the materials to be operated upon, whereby estimation can be made of the solubilities of such impurities.

When the lead oxide content of the slimes which are being treated has gone into solution in the leaching tank the circulation of the acetic acid water solution is stopped and the slime pulp is allowed to settle. Subsequently the clear solution so derived is liltered olf, and the residue of the slimes leaching operation is water washed to free it of acetates. n Should the said washed slimes residue contain payable values of gold or silver it is operated for same by any well known metallurgical method whereby the gold and silver value contents are recovered. The wash solution from the treatment of the residue of the slirnes is fed to a water storage tank andV is utilized later as wash Water in a further (following day) cycle, whilst theV clear solution fromV the slimes leaching operationis. passed direct to the sands contained 1n theV separate leaching tank provided therefor.

' Circulation of the clear solution is carried on 1n the charge of sands material or pulp 1n the leaching tank therefor until the lead and vzinc oxide contents of said sands have gone into solution.

Said sands pulp is then allowed to settle, and the clear solution resulting from the settling operation is subsequently filtered off, whilst the residue thereof is washed with water containing free acetic acid, then with water only to free it of acetates. Should such washed residue contain payable values of gold or silver it is operated on by any well known metallurgical method to extract therefrom such values. rEhe wash solution de- Y rived from water washing the said residue is any) - `Where the material which is being treated has not been separated into sands and slimes for the treatment of these products in separate leaching tanks, but is subjected to the leaching treatment described in one tank, the clear solution derived from suoli latter leaching treatment of the material is fed to the said precipitating tank.

Y Such clear solution in the said precipitating tank is then subjected to treatment by forcing thereinto sulphur dioxide gas'with the object of precipitating from the solution the lead acetate contained therein as lead sulphite. Said treatment is continued until a part of the whole of the lead acetate is precipitated from the solution and the acetic acid of the solution is regenerated for further use in another cycle of operation. Precipitate remaining aftersuch treatment is allowed to settle when the clear solution resulting from the settling operation is filtered oif and the precipitated sulphite ofV lead is water washed to free it of acetates. Water wash from such operation is passed to wash water storage tank for further (next day) use. Said treatment ensures the production of pure sulphite of lead. .The sulphite of lead so derived is subsequently melted out of Contact with air to convert it to lead oxide and the molten mass which may also contain a small proportion of metallic lead has carbon added thereto whereby the lead content CTI ofthe mass is then converted into metallic of the solution is decomposed and carbonate of lead is thus produced. ln such case the remaining lead acetate of the solution is precipitated therefrom` by utilizing sulphur dioxide gas which is forced thereinto whereby sulphite of lead is produced and thel acetic acid of the solution is regenerated.

As a further alternative, insteadk of precipitating the lead acetate fromthe said clear solution by sulphur dioxide gas, the said solution may be treated with sulphuric acid whereby the lead is obtainable as lead sulphate and the acetic acid of the solution is regenerated for further use.

Precipitation of the lead from the said clear acetate solution may alsobe eifected by subjecting such solution to electrolytic treatment, whereby lead is obtained in the metallic state. In such treatment the electrolyte solution is alkaline or approximately alkaline and carbon or insoluble anodes and lead or iron or aluminium cathodes are utilized.

The clear solution derived from the sett-ling` operation of the lead sulphite precipitate produced as above described, and which conlll) lil

sists of a solution ot regenerated acetic acid and acetate of Zinc, is then treated to reduce it to the neutral point with linely powdered carbonate ot lime, or carbonate ot barium,

l 'and subsequently it is treated to reduce it to slightly beyond neutral point- With hydrated oxide ot lime or barium hydrate. Atmospheric air is now injecter through the said solution in presence ot' a calculated percentage ot oxide or" Zinc, whereby iron and other impurities in the solution arc precipitated there from. Should there be traces ot copper present in the solution the latter (before it is neutralized) has circul .red therein metallic Zinc, whereby the copper is piecipitated trom the solution.

Subsequently the solution is iiltered and the resioue is Water Washed to free it ot acetates. Said Wash Water is then passed to a separate Wash Water storage tank tor further (following day) use. The clear filtered solution which consists of a neutral solution ot lime and zinc acetatcs is operated on by electrolysis, whereby zinc is obtained in the metallic state, and the acetic acid is subsequently regenerated for further use. During electrolysis ot Zine acetate acetic acid is being erat-ed and lime or barium oxide is added to electrolyte to keep solution nearly neutral.

Upon the separation of the zinc troni the electrolytically treated solution, the electrolyte is bye-passed and sulphuric acid is added thereto to enable precipitation therefrom ot calcium or barium sulphates and the acetic acid regenerated. The regenerated acid solution upon being filtered and having acetate of lead added thereto, so that tree sulpliuic acid in the solution Will be decomposed, is made available for use in another cycle of operation in the treatment of new material.

Instead ot subjecting the clear solution derived from the settling operation ot' the lead sulphite precipitate to treatment as above described to obtain metallic Zinc, the Zinc contents oi' such solution may be precipitated therefrom by adding to the solution sulphuretted hydrogen gas, or a calculated percentot calcium sulphide, or barium sulphide, whereby sulphide of Zinc is produced, the latter being subsequently roasted to provide oxide ot zinc.

The calcium or barium passes into solution as acetates; such solution is filtered oli and has added thereto sulphuric acid whereby the calcium or barium acetates of the solution are precipitated therefrom and the acetic acid of the solution is regenerated. Or, the said clear solution derived trom the settling operation ot the lead sulphite precipitate maybe treated to obtain oxide or" zinc, by neutralizing the tree acetic acid ot the solution by adding to the solution powdered calcium or barium carbonate; the solution has then added to it calcium or barium hydrate,

rev-ensulph: ics; the clear solution is iiltered and the regenerated acetic acid solution has d thereto a small proportion ot acetate ad to decompose any excess ot sulphuric rlhe resultant solution is then available another cycle on iresli material. T o residue et hydrates, ammonium hydrate is added Which dissolves the hydra-ted Zinc and zine ammonium solution is thus produced; such solution is iiltered and the filtrate is then transferred to a still, and steam injected thercinto, to drive oil1 the ammonium hydrate, which isccondensed tor future use; the contents ot the still are deprived ot Water, Where by zinc oxide is produced.

in the operation et the process itis necessarlY in the Washing operations oi the leached mate al, that the iii-st and second Wash Waters contain a proportion ot tree acetic acid. other .vise a little hydrated oxide ot lead will be lett with the material.

.fis acetic acid is miscible with Water in all iropoitions, it' the 7ater ot the acetic acid 4elution used in the process is likely to v crate iii the operation ot' the process due o the exposure of the solution ot acetic acid n .vatcr to heat or Wind, the tanks containing such solution should be covered, or such tanks should be provided vvitli a movable cover having a Water seal. Protection ot the solution trom such evaporation is not necessary vvnen the solution has been used to act on any linie, iron, magnesia, Zinc or other elements to torni neutral acetates oi" all or any of such elements, as the evaporation in such case only results in the concentration orn the solutions ot acetates.

treatment ot material by the process above described, it Will be found that practically all the silver and gold contents ot' the leached material remain therewith except vhen sulpiiate ot silver has been formed in C; ot the material. In such case the roasteoL naterial is leached with hot Water in place ot cold water to dissolve sulphate oi silver and the other soluble salts. The soluble sulphate of silver is precipitated out ot solution iviti sodium chloride. Further, in correspondence With greater or lesser percentage oi silica, iron, alumina, and other im- |ies which remain in the leaclied residue ie material originally operated on by the yelution ot acetic acid in Water, so the gold ind silver contents in the material operated n vvill be found to be more or less a concenrated product ot gold or silver. Further, eac produced 'trom the operation ot the orocess is practically tree ot zinc and silver, .nd contains practically no impurities it to treat itby refining methis not necessaryv ods to provide soft pig lead. Again, if electrolytic. zinc is produced through the process it is of high grade and free of impurities.

Moreover, in every stage of the said process the acetic acid which is utilized therein is capable of regeneration for further use again Vand again in cycle of operations without any appreciable loss. The operation of the proccss further ensures the obtaining of a high degree of extraction of the lead and Zinc contents of the material which is treated, and

that the capital outlay for metallurgical plant will be less than that required for present known methods of treating the material by wet: concentration, smelting and -rening Further, if costs are excessive in the provision of electric power for the electrolysis of zinc, the process herein described allows of the treatment of original material, whereby concentrated product-s of high grade sulphide or oxide of zinc can be made available for transportation to places whereelectric power costs are low.

During the operation of the process sulphur dioxide gas is set free when sulphite of lead is melted to produce oxide of lead and "also when zinc sulphide is roasted to provide zinc oxide. Such gas may be utilized in the precipitation of lead sulphite from the lead acetate solution derived from the operation of the process.

Throughout this specification reference l'has been made to acetic acid. It is to be understood, however, that pyroligneous acid or wood vinegar may be substituted for such acid.V These remarks apply also t the use of the term acetic acid in the appended claims.

In the accompanying drawing the operation of the process is illustrated diagrammatically, also a suitable roasting furnace 2. A vat 3 is adapted to receive the ground material and withinwhich soluble salt-s thereof may be dissolved. There. is a water storage tank 4 leading to the vat 3 and also to the mechanical .separating appliance 5.

I There is also a filter 18 associated with the tank and with said filter a furnace 19 for melting lead sulphite.

The purifying tank 2O is furnished for treating clear'solution from settling operation of lead sulphite precipitate, storage means 21 being provided for carbonate of a ,grinding unit 1 being provided, Y

lime or barium, and storage means 22 for hydrated oxide of lime or barium hydrate, and also storage means 23 for oxide of zinc. Such storage means 21, 22 and 23 together with air compressor plant 24 and filter 25 are associated with the tank 20. Waste from the filter 25 may be discharged through the connection 35.

Prccipitating tank 26 or elect-rolytic apparatus 27 for obtaining metallic Zinc can also be provided, the tank 26 having associated therewith the iilter-28- Another precipitating tank 29 for calcium or bariumsulphates is connected to the filter 28 and such tank 29 lis also connected to storage means 30 for sulphuric acid. The tank 29 is also connected to a filter 31 having waste connection 32 for calcium or barium sulphates. i There Vare separate series 33 and 34 of wash water storage tanks leading to separate filters where reuired.

llVhat I claim as my invention and desire to secure by Letters Patent is 1. Process of treatingv materials containing lead and zinc values which comprises grinding and water pulping the material and subsequently agitating same whereby the soluble salts thereof are dissolved, removing the water from the material, leaching said dewatered material in a circulating solution of acetic acid in water whereby oxides of lead and Zinc are dissolved and acetates of lead and Zinc are formed, stopping the circulation of said solution and allowing the leached material pulp to settle, withdrawing the clear solution derived from said settling operation and filtering the same, waterwashing the material residue to free it of acetates, passing the said clear filtered solution to a precipitating` tank, and treating said solution in said tank whereby at least a part of the lead acetate content thereof is converted to lead sulphite and the acetic acid of the solution is regenerated for further use.

2. Process of treating materials containinglead and zinc values which comprises grinding and water pulping the material and subsequently agitating same whereby the soluble salts thereof are dissolved and the material is separatedintoslimes and sands, removing the water from the sands and slimes, leaching said slimes in a circulating solution of acetic acid in water whereby oxides of lead and zinc are dissolved and acetates of lead and Zinc are formed, stopping the circulation of said solution and allowing the leached slimes pulp to settle, withdrawing the clear solution derived from said settling operation and filtering the same, water washing' the slimes residue to free it of acetates, passing the said filtered clear solution direct to said sands and circulating said solution in said sands whereby a pulp thereof is formed and continuing said circulation until the oxide of lead and zinc contents have dissolved, subsequently alloo lowing said sands pulp to settle, withdrawing the clear solution from said sands pulp and filtering same, washing the sands residue to free it of acetates, passing the clear liltered solution derived from said sands pulp to a precipitating tank, and treating said solution in said tank whereby at least a part of the lead acetate content thereof is converted to lead sulphite and the acetic acid of the solution is regenerated for further use.

3. Process of treating materials, in which the acetic acid solution according to claim l contains approximately 0.3 lbs. of acetic acid to each lb. of lead oxide present in the material and 1.5 lbs. of acetic acid to each lb. of zinc oxide present in the material.

4. Process of treating materials according to claim l, in which the clear iltered acetate solution is subjected to treatment in the precipitating tank by forcing sulphur dioxide gas thereinto whereby at least a part of the lead acetate content thereof is converted to lead sulphite and the acetic acid of the solution is regenerated for further use.

5. Process of treating materials in which lead sulphite is produced according to claim 1, and in which the resultant pulp from the lead sulphite production stage of the process is allowed to settle, withdrawing and filtering the clear solution derived from said settling operation, water washing the residual lead sulphite to free it of acetates and by-passing said wash water to a storage tank therefor.

6. Process or" treating materials in which lead sulphite is producedaccording to claim l, and in which the resultant pulp from the lead sulphite production stage of the process is allowed to settle, withdrawing and ltering the clear solution derived from said settling operation, water washing the residual lead sulphite to free it of acetates, and subsequently melting the derived lead sulphite to convert it to lead oxide, the molten mass having carbon added thereto whereby metallic lead is thus produced.

In testimony whereof I alii'x my signature.

VLLIAM HENRY CORBOULD. 

